Studies on the regulation of glycogen synthase phosphorylation in vitro and in vivo will be continued. Glycogen synthase will be purified from muscle of control and hormone-treated rabbits. The purified enzyme will be characterized in terms of phosphate content and kinetic properties. A calmodulin-dependent synthase kinase will be purified from rabbit liver and characterized in terms of structure and substrate specificity. The phosphorylation state of a protein inhibitor of phosphoprotein phosphatase will be studied in perfused rat muscle. Effects of insulin and epinephrine on the phosphorylation state will be determined.